1. Field of the Invention
The present invention relates generally to electrical switching apparatus and, more particularly, to a locking assembly for the operating handle of a circuit breaker.
2. Background Information
Electrical switching apparatus include, for example, circuit switching devices and circuit interrupters such as circuit breakers, contactors, motor starters, motor controllers and other load controllers.
Circuit breakers are generally old and well known in the art. An example of a circuit breaker is disclosed in U.S. Pat. No. 5,341,191. Circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high level short circuit or fault condition. Molded case circuit breakers, for example, include at least one pair of separable contacts which are operated either manually by way of a handle disposed on the outside of the case or automatically by way of an internal trip unit in response to an overcurrent condition.
Circuit breakers typically have two or three possible operating handle positions, corresponding to the status of the separable contacts. For example, these positions may include an ON position, in which the separable contacts are closed, an OFF position in which the contacts are open, and a tripped position in which the contacts are tripped open. Typically, the handle position corresponding to the tripped position of the contacts is in between the ON and OFF positions.
In circuit breaker installations, for example in a panel board or load center, it is often desirable or essential that the settings of a single circuit breaker, or a group of circuit breakers, remain undisturbed. Unauthorized or inadvertent changing of the position of these breakers could result in annoying interruptions to service or operations, serious damage to an electrical apparatus, or even serious harm to a person. For example, accidental actuation of a circuit breaker might result in electrocution or shock to a workman performing electrical work or repair within an office building or home. Therefore, to prevent, for example, another person from inadvertently returning the circuit breaker handle to the ON position when a worker is doing electrical work in an area other than the immediate vicinity of the circuit breaker box or electrical panel, safety measures must be taken. One such safety measure is the addition of a locking assembly to prevent displacement of the circuit breaker handle.
Although the main purpose of a circuit breaker is to trip during overload or short circuit conditions in order to protect downstream equipment and electrical wiring from damage, it may also be highly desirable to inhibit the circuit interruption function under certain conditions where, for example, the potential fire hazard of a non-opening circuit breaker is deemed to be a lesser hazard than if current flow to downstream devices is interrupted. The decision to accept the risk of fire over some other hazardous consequence may occur during emergencies or other critical situations where loss of life might occur if power is disrupted. Conceivable situations include, for example, circuit breakers employed in connection with combat (e.g., in a battleship under wartime conditions), fire-fighting (e.g., energizing pumps for pumping water to fire hoses in a high-rise building), spacecraft launch (e.g., energizing ground-based circuits critical to a safe launch), mining (e.g., energizing pumps employed to rapidly remove water from a flooded mine shaft), or nuclear power generation (e.g., energizing circuits critical to tripping a nuclear reactor). Sce, for example, U.S. Pat. No. 5,831,503. Although most circuit breakers can still trip internally even if the handle is held in the on position, a handle lock to prevent displacement of the circuit breaker handle would preclude manual operation that might inadvertently remove power in a critical situation.
U.S. Pat. Nos. 2,849,552; 3,214,530; 3,408,466; 4,347,412; 5,147,991; 5,219,070; 5,310,969; 5,412,167; 5,500,495; 5,577,599; and 5,732,815 disclose handle locking mechanisms consisting of an assembly of at least two parts and each employs a padlock to lock the handle of the circuit breaker in a fixed position. There are several disadvantages associated with known handle locking mechanisms of this type.
Many known locking mechanisms of this type employ a set or Allen screw to engage the circuit breaker handle, in order to prohibit its movement. See, e.g., U.S. Pat. Nos. 2,849,552; 5,147,991; 5,500,495; and 5,732,815. Construction of the locking mechanisms is typically complex and often comprises numerous, separate parts. Generally, the locking mechanisms are not integrated with the circuit breaker, thereby being susceptible to loss of one or more pieces when not in use. Applicability is often limited to a certain type of circuit breaker or a select type or shape of circuit breaker handle and modification to the circuit breaker handle and/or the circuit breaker housing is frequently required. See, e.g., U.S. Pat. Nos. 4,347,412; 3,408,466; 5,219,070; and 5,412,167. Many known locking mechanisms of this type also employ at least one nose, wedge, end part, leg or similar structure adapted for insertion within the handle opening of the circuit breaker housing, for example, between the circuit breaker handle and the end wall of the handle opening, to abut, underlie or otherwise engage the end wall, in order to resist movement of the circuit breaker handle. See, e.g., U.S. Pat. Nos. 2,849,552; 3,408,466; 4,347,412; 5,412,167; 5,500,495; and 5,732,815.
There is a need, therefore, for a simplified locking assembly for electrical switching apparatus that requires no modification or invasive engagement of the electrical switching apparatus handle or housing.
Accordingly, there is room for improvement in locking assemblies for electrical switching apparatus.
These needs and others are satisfied by the present invention, which is directed to a locking assembly for an electrical switching apparatus. The locking assembly engages an elevated portion of the apparatus housing in order to restrain movement of the operating handle. The locking assembly may employ a wide variety of user supplied locks to restrain movement of the operating handle.
As one aspect of the invention, a locking assembly is used with an electrical switching apparatus, which includes a housing with an opening and an operating handle protruding from the opening, the locking assembly comprises: a first locking element pivotally connected to and extending away from the operating handle in a first direction, in order to engage a portion of the housing, the first locking element including a first aperture extending therethrough; a second locking element pivotally connected to and extending away from the operating handle in a second direction opposite the first direction of the first locking element, in order to engage another portion of the housing, the second locking element including a second aperture extending therethrough, the second aperture corresponding to the first aperture of the first locking element; and a lock extending through the first and second apertures, in order to lock the first and second locking elements, respectively, thereby restraining movement of the operating handle.
As another aspect of the invention, a locking assembly is used with an electrical switching apparatus, which includes a housing with an elevated portion having a top, two sides, opposing first and second edges and an opening, the opening including a first end and a second end, the electrical switching apparatus also including an operating handle protruding from the opening, the operating handle moving between a first position proximate the first end of the opening and a second position proximate the second end of the opening, the locking assembly comprises: a lock having a shackle; a first locking element including at least one first aperture receiving the shackle of the lock, the first locking element structured to engage one of the opposing first and second edges of the elevated portion of the housing, in order to restrain movement of the operating handle; a second locking element including at least one second aperture corresponding to the at least one first aperture of the first locking element, the second locking element being structured to engage at least a portion of the top of the elevated portion of the housing, in order to further restrain movement of the operating handle; and means for pivotally connecting each of the first and second locking elements to the operating handle.
The first locking element may have an L-shape corresponding to at least a portion of the elevated portion of the housing. The L-shaped first locking element may include a first portion with an edge-engaging portion structured to engage a corresponding one of the opposing first and second edges of the elevated portion of the housing.
The first locking element may have a T-shape with a portion thereof corresponding to at least a portion of the elevated portion of the housing. The T-shaped first locking element may include symmetrical first and second edge-engaging portions each of which is structured to engage a corresponding one of the opposing first and second edges of the elevated portion of the housing.
The T-shaped locking element may be adapted to pivot between a first locked position and a second locked position, in order to restrain movement of the operating handle between the first position and the second position, respectively, of the operating handle.
As another aspect of the invention, an electrical switching apparatus comprises: a housing including at least one elevated portion having a top, two sides, opposing first and second edges and at least one opening, the at least one opening having a first end and a second end; at least one pair of separable contacts; an operating mechanism including at least one operating handle structured to open and close the separable contacts, each of the at least one operating handle protruding from a corresponding one of the at least one opening of the at least one elevated portion of the housing and moving between a first position proximate the first end of the corresponding one of the at least one opening and a second position proximate the second end of the corresponding one of the at least one opening; and an integral locking assembly comprising: a lock having a shackle; a first locking element including at least one first aperture receiving the shackle of the lock when the first locking element engages a corresponding one of the opposing first and second edges of at least one of the at least one elevated portion of the housing, in order to restrain movement of the at least one operating handle; a second locking element including at least one second aperture corresponding to the at least one first aperture of the first locking element and receiving the shackle of the lock when the second locking element engages at least a portion of the top of at least one of the at least one elevated portion of the housing, in order to further restrain movement of the at least one operating handle; and means for pivotally connecting each of the first and second locking elements to at least one of the at least one operating handle.